It has been demanded that LCD projectors and other projection displays have a small structure and offer high brightness, high contrast, and other favorable performance characteristics.
A conventional technology for brightness enhancement is disclosed, for instance, by Japanese Patent Laid-open No. H4-63318. When an LCD panel is used as a video display device, this technology uses a polarizing beam splitter to separate a random polarized light emission from a light source into p-polarized light and s-polarized light, and projects them onto the LCD panel with their polarization directions aligned. A conventional technology for contrast enhancement is disclosed, for instance, by Japanese Patent Laid-open No. H6-342158. This technology uses a lens having a concave conical surface and converts light rays, which come from a reflector and have a great incidence angle, into parallel rays. A conventional technology for screen brightness uniformity enhancement is disclosed, for instance, by Japanese Patent Laid-open No. H3-111806. This technology describes an integrator optical system, which uses two array lenses.